1. Field of the Invention
The present invention relates to a switch, and more particularly to a safety switch that is mounted on a power strip including a power-supplying circuit and is capable of cutting off the power-supplying circuit when circuit current on the power-supplying circuit is too high.
2. Description of Related Art
Electric appliances connect to and obtain power from electrical outlets. However, electrical outlets are usually mounted securely in a wall or floor and cannot be moved. Therefore, an electric appliance having a wire and plug connected to the electrical outlet had to be positioned near the electrical outlet. As the number of electrical appliances proliferated to include lamps, TVs, tape and disk players, stereos, clocks, computers, computer peripherals, etc., electrical outlets in rooms is insufficient to connect multiple electric appliances.
Therefore, a power strip having multiple receptacles and an extended cable was developed. The power strip is connected to an electrical outlet, and multiple electric appliances are connected to the power strip. The extended cable allows an electric appliance to be positioned as desired without being limited by the electrical outlet in the wall. To prevent excessive current from developing in and destroying the power strip when total power consumption of the electric appliances connected to the power strip exceeds a maximum load of the power strip, multiple safety switches are mounted on the power strip and connect respectively to the receptacles.
With reference to FIGS. 7 and 8, a conventional safety switch has a casing (90), a first prong (91), a second prong (92), a switch contact (93) and a rocker (94).
The casing (90) is hollow, is mounted on a power socket and has a top, a bottom and a cavity. The first and second prongs (91, 92) are mounted in the cavity, extend down through the bottom of the casing (90) and are connected to a power-supplying circuit in the power strip. The switch contact (93) is bimetallic, bends upward as temperature of the switch contact (93) increases, is connected to the second prong (92) and has a proximal end and a distal end (931). The proximal end is connected securely to the second prong (92) in the cavity, and the distal end (931) selectively abuts the first prong (91). The rocker (94) is mounted pivotally on the top of the casing (90) and has a first end, a second end and an arm (941). The arm (941) is mounted on the first end of the rocker (94), extends through the top of the casing (90) and is connected to the distal end (931) of the switch contact (93). Pressing the first end of the rocker (94) pushes the arm (941) and the distal end (931) down so the distal end (931) of the switch contact (93) contacts the first prong (91) and activates the power-supplying circuit. When the current in the power-supplying circuit is too high and the temperature of the switch contact (93) increases excessively, the switch contact (93) bends due to the bimetallic characteristic, and the distal end (931) pulls away from the first prong (91) to deactivate the power-supplying circuit.
However, environmental temperature in high latitude areas such as the Temperate Zone and the Frigid Zone is very low and may even be below 0° C. In such a severely cold environment, the temperature of a heated switch contact (93) separated from the first prong (91) due to over current quickly drops and causes the distal end (931) to contact the first prong (91) again after a very short time from the separation of the first and switch prongs (91, 93). Such repetitive contact and separation of the first and switch prongs (91, 93) improperly turns the electric appliances connected to the power strip on and off. The electric appliances and may probably burn out.
To overcome the shortcomings, the present invention provides a safety switch to mitigate or obviate the aforementioned problems.